Satellite signal receiver

ABSTRACT

A satellite signal receiver includes a satellite signal reception unit, timer, and power-on/off controlling element. The satellite signal reception unit calculates a current position of the satellite signal receiver using an electric wave from a satellite, in response to a positioning request. The timer is used to clock an elapsed time in calculating the current position of this receiver. The power-on/off controlling element controls an on/off state of power supplied to both the satellite signal reception unit and the timer on the basis of information including the positioning request, the elapsed time clocked by the timer, and a reception condition of the satellite signal reception unit. Accordingly, a period of time for supplying the power is automatically turned on/off to be shortened in cases the positioning is impossible, thus the power being saved.

Background of the Invention

[0001] 1. The Field of the Invention

[0002] The present invention relates to a satellite signal receiver, andin particular, to a power controller for a satellite signal receiverused for devices, such as mobile terminals or mobile phones, that have asatellite signal reception unit.

[0003] 2. Related Art

[0004] One conventional satellite signal receiver is known by JapanesePatent Laid-open Publication No. 8-304526, of which configuration isillustrated by FIG. 1.

[0005] The satellite signal receiver shown in FIG. 1 includes apositional information generator 1, operational command receiver 2,power supply 3, and power switching unit 4 that turns on or off power ofthe positional information generator 1.

[0006] The positional information generator 1 is equipped with anreceiving antenna 5 for receiving electric waves that has beentransmitted from satellites, satellite receiver 6, positional dataoutput circuit 7, and transmitting antenna 8. The satellite receiver 6demodulates a signal of the received electric waves to computes acurrent position of this apparatus. The operational command receiver 2includes a receiving antenna 9 for receiving in wireless an operationalcommand that has been received from the manager, and a reception circuit10 via the receiving antenna 9.

[0007] When the receiver is in operation, only the power of theoperational command receiver 2 is turned on to wait for receiving anoperational command from the manager. When the manager transmits anoperational command, the operational command receiver 2 receives theoperational command and activates the power switching unit 4 so that itturns on. This unit 4 operates to supply the power from a power supply 3to each element of the positional information generator 1, so that eachelement is energized. The satellite receiver 6 demodulates eachsatellite signal supplied from the antenna 5 in such a manner that acurrent position of this receiver is computed based on the signals froma plurality of satellites. The computed positional data are the subjectto demodulation in the positional data output circuit 7, before beingsent to the manager via the transmission antenna 8.

[0008] After the positional information generator 1 generates positionaldata, the power switching unit 4 will be kept to be on for a certaintime, intermittently, or until receiving a command for stopping theoperation. During the period of the on-state of the power switching unit4, the generator 4 generates positional data.

[0009] According to this satellite signal receiver, if there is no needfor demands for positional information, powering a main part of theapparatus is stopped, while the power is prepared whenever it isnecessary. Hence consumption of useless power is suppressed.

[0010] However, the foregoing satellite signal receiver is configured sothat an external command controls the turn on/off of power of thesatellite receiver 6. Therefore, even when this receiving apparatus islocated such that it is impossible for this apparatus to receivesatellite electric waves or it is extremely difficult for this apparatusto perform such reception, thereby positioning being impossible, theexternal command causes the satellite receiver to be activated. Thisresults in that the power is consumed uselessly.

SUMMARY OF THE INVENTION

[0011] An object of the present invention is to provide, with dueconsideration to the drawback of such a conventional satellite signalreceiver, a power supply controller for a satellite signal receiver,which is able to control operational conditions of a satellite receiverdepending on positioning conditions.

[0012] In order to accomplish the above object, the present inventionprovides satellite signal receiver comprising: a satellite signalreception unit for calculating a current position of the satellitesignal receiver using an electric wave from a satellite, in response toa positioning request; a timer for clocking an elapsed time incalculating the current position of the satellite signal receiver; andpower-on/off controlling means for controlling an on/off state of powersupplied to both the satellite signal reception unit and the timer onthe basis of information including the positioning request, the elapsedtime clocked by the timer, and a condition under which the satellitesignal reception unit receives the signal from the satellite.

[0013] Preferably, the power-on/off controlling means includes: switchmeans for switching on or off the power supplied to both the satellitesignal reception unit and the timer; and control means for controllingturn on/off operations of the switch means based on the information. Itis also preferred that the information about the condition isinformation about the number of ephemerides. In this case, preferably,the control means includes first control means for turning on the switchmeans in response to the positioning request, setting means foradjustably setting a period of active time counted from a first timeinstant at which the switch means turns on to a second time instant atwhich the satellite signal reception unit calculates the currentposition, and second control means for turning off the switch means whenthe elapsed time reaches the period of active time. By way of example,the setting means is configured so that larger the less the number ofephemerides, the larger the period of active time.

[0014] Still preferably, the information about the condition isinformation about an elapsed time from the last calculation of thecurrent position.

[0015] As a further configuration according to the present invention,there is provided a satellite signal receiver comprising: a satellitesignal reception unit for intermittently calculating a current positionof the satellite signal receiver at adjustable intermittent intervals byusing an electric wave from a satellite; a timer for clocking an elapsedtime every time when the current position of the satellite signalreceiver is calculated; and power-on/off controlling means forintermittently controlling an on/off state of power supplied to thesatellite signal reception unit on the basis of information includingthe elapsed time clocked by the timer every time when the currentposition of the satellite signal receiver is calculated.

[0016] According to the above constructions, the power supplied to boththe satellite signal reception unit and the timer, or to the satellitesignal reception unit is turned on in response to a positioning requestissued or at intermittent intervals. During such supply of the power,the power can be turned on/off to control a period of time for supplyingthe power or intermittent intervals for supplying the power, accordingto information held by the satellite signal reception unit or itsreceiving condition. Thus, in cases the satellite signal receiver isplaced at situations in which the positioning is impossible, the timefor supplying of the power is shortened to avoid useless consumption ofthe power.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In the accompanying drawings:

[0018]FIG. 1 is a block diagram showing the configuration of aconventional satellite signal receiver;

[0019]FIG. 2 is a block diagram showing the configuration of a satellitesignal receiver employed in a first to fifth embodiments of the presentinvention;

[0020]FIG. 3 is a flowchart depicting control of power in the satellitesignal receiver according to the first embodiment;

[0021]FIG. 4 is a flowchart depicting control of power in the satellitesignal receiver according to the second embodiment;

[0022]FIG. 5 is a flowchart depicting control of power in the satellitesignal receiver according to the third embodiment;

[0023]FIG. 6 is a flowchart depicting control of power in the satellitesignal receiver according to the fourth embodiment;

[0024]FIG. 7 is a flowchart depicting specification of a period ofactive time necessary for power control conducted in the satellitesignal receiver according to the fifth embodiment;

[0025]FIG. 8 is a block diagram showing the configuration of a satellitesignal receiver employed in a sixth and seventh embodiments of thepresent invention;

[0026]FIG. 9 is a flowchart depicting control of power in the satellitesignal receiver according to the sixth embodiment; and

[0027]FIG. 10 is a flowchart depicting control of power in the satellitesignal receiver according to the seventh embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Embodiments of the present invention will now be described inconjunction with the appended drawings.

[0029] (First Embodiment)

[0030]FIG. 2 is a block diagram showing the configuration of a satellitesignal receiver in accordance a first embodiment of the presentinvention. Incidentally, a satellite signal receiver used in a second tofifth embodiments, which will be described later, also adopt theidentical configuration to that shown in FIG. 2.

[0031] As shown in FIG. 2, the satellite signal receiver is equippedwith an antenna 5, satellite signal reception unit 6, timer 11,communication unit 13, power supply 3, power switching unit 4, andcontrol unit 12.

[0032] Among these constituents, the antenna 5 is placed to receive anelectric wave from a satellite. The satellite signal reception unit 6has a memory device 14 to store various types of information and a clockdevice 15 to clock a positioning time instant, and performs signaldemodulation processing on the received electric wave to calculate acurrent position of this satellite signal receiver.

[0033] The communication unit 13 conducts communication with a certainexternal system in such a manner that it not only receives a positioningrequest from the external system but also transmit to the externalsystem date of a calculated current position. The power switching unit 4turns on/off power supplied from the power supply 3 to both thesatellite signal reception unit 6 and the timer 11. The control unit 12controls the operation of each unit. A time instant to turn on/off thepower switching unit 4 is controlled by the control unit 12 based oninformation involving an elapsed time measured by the timer 11.

[0034] The operation of the satellite signal receiver in accordance withthe first embodiment of the present invention will now be described inconjunction with FIGS. 2 and 3. FIG. 3 is a flowchart showing powercontrol conducted in the satellite signal receiver. The control unit 12executes the processing shown in FIG. 3.

[0035] When the control unit 12 receives a request for positioning froman external system through the communication unit 13 (step 100), thecontrol unit 12 turns on the power switching unit 4 to activate both thesatellite signal reception unit 6 and the timer 11 (step 101).

[0036] By the way, the positioning of the satellite signal receiver isnot always possible, and it mostly depends on circumstances to receivethe electric waves from satellites. Thus, a period of activity time (aperiod to time-out) counted from the turn-on of the power switchingmeans 4 to the calculation of a current position of this satellitesignal receiver (positioning), specifically, the output of positionalinformation from the satellite signal reception unit 6, is specified inadvance. A period of time to the expected next positioning usuallyvaries depending on the number of ephemerides, which is stored by thememory device 14 of the satellite signal reception unit 6 undercontinuous supply of power from the power supply 3.

[0037] Therefore, the control unit 12 acquires information in relationto the number of ephemerides stored by the memory device 14 (Step 102),then determines if there is any difference between the number ofephemerides and a given threshold of number (step 103). Depending onthese determined results, the control unit 12 performs a process tochange the period of activity time from a time instant at which thepower supply switch unit 4 is turned on to a time instant when thecontrol unit 12 acquires positioning information.

[0038] In the example of FIG. 3, the period of activity time isspecified as T01#short when the number of ephemerides is equal or largerto or than its given threshold (step 104). In contrast, the period ofactivity time is specified as T01#long (>T01#short) when the number ofephemerides is smaller than the threshold (step 105). Alternatively,this determination may involve three or more stages with two or morepieces of thresholds.

[0039] Subsequently, the control unit 12 compares a period of elapsedtime measured by the timer 11 with the period of activity time (step106). When the measured period of elapsed time becomes equal or largerto or than the period of activity time with no calculation of a currentposition of this satellite signal receiver made by the satellite signalreception unit 6, the control unit 12 regards the positioning as beingimpossible. In this case, the control unit 12 turns off the powerswitching unit 4 (step 107), then notifies the not-shown external systemof an unsuccessful positioning through the communication unit 13 (step108).

[0040] In contrast, in cases where the period of elapsed time measuredby the timer 11 is smaller than that of the period of activity time, thecontrol unit 12 tries to acquire positioning information from thesatellite signal reception unit 6 (step 109). Then the control unit 12begins a process to determine whether the positioning has been finishedor not (step 110). When the positioning has been finished, the controlunit 12 sends an “off” commands to the power switching unit 4 (step111), and outputs the positioning information to the not-shown externalsystem via the communication unit 13 (step 112). If the positioning hasnot been finished yet, the control unit 12 returns to the process atstep 106 to repeat the foregoing processing.

[0041] As explained above, in the satellite signal receiver according tothe first embodiment of the present invention, the period of activitytime is adjusted depending on information about the number ofephemerides stored by the memory device of the satellite signalreception unit. Thus the period of activity time can be approached ormade to agree to or with a remaining period of time to the nextpositioning to be expected as closer as possible. It is thereforepossible to shorten a period of time to power the satellite signalreception unit under a condition the positioning cannot be conducted,thus reducing useless consumption of the power.

[0042] (Second Embodiment)

[0043] Referring to FIGS. 2 and 4, a second embodiment of the presentinvention will now be described.

[0044] A satellite signal receiver according to the second embodimentdiffers only in that the control unit 12 and the satellite signalreception unit 6 are constructed to perform a further series ofprocessing different from that in the first embodiment. The remainingconfiguration and operations of this satellite signal receiver areidentical to those in the first embodiment, so the differences withrespect to the processing and operations are mainly described.

[0045]FIG. 4 is a flowchart showing power control for the satellitesignal receiver according to the second embodiment, which is executed byboth of the control unit 12 and the satellite signal reception unit 6.

[0046] When receiving a request for positioning issued outside throughthe communication unit 13 (step 200), the control unit 12 turns on thepower switching unit 4 in order to activate both of the satellite signalreception unit 6 and the timer 11 (step 201).

[0047] By the way, a period of elapsed time counted from a time instantwhen the clock device 15 counted a positioning time at the lastpositioning conducted by the satellite signal reception unit 6 has alsoinfluence on a period of time to the next positioning to be expected.Considering this fact, in the satellite signal reception unit 6 of thepresent embodiment, a time instant clocked by the clock device 15 at acertain positioning is memorized by the memory device 14.

[0048] Therefore, based on the current time instant clocked by theincorporated clock device 15 to which the power supply 3 supplies poweranytime and the last positioning time instant memorized by the memorydevice 14, the satellite signal reception unit 6 calculates a period ofelapsed time from the last poisoning time instant (step 202). Thecalculated period of elapsed time is sent to the control unit 12.

[0049] Responsively to reception thereof, the control unit 12 will moveto processing to adjust the period of activity time counted from a timeinstant when the power is turned on to a time instant when positioninformation is obtained (step 203). Specifically, it is determinedwhether or not the calculated period of elapsed time from the lastpositioning is equal or larger to or than a given threshold set for theperiod.

[0050] In the example of FIG. 4, the period of activity time isspecified as T02#long when the period of elapsed time is equal or largerto or than its given threshold (step 204). In contrast, the period ofactivity time is specified as T02#short (<T02#long) when the period ofelapsed time is smaller than the threshold (step 205). Alternatively,this determination may involve three or more stages with two or morepieces of thresholds.

[0051] Subsequently the control unit 12 determines whether or not theperiod of elapsed time measured by the timer 11 is equal or larger to orthan the period of activity time (step 206). If the period of elapsedtime measured by the timer 11 is equal or larger to or than the periodof activity time with no calculation of a current position of thissatellite signal receiver, the control unit 12 regards the positioningas being impossible. In this case, the control unit 12 turns off thepower switching unit 4 (step 207), then notifies the not-shown externalsystem of an unsuccessful positioning through the communication unit 13(step 208).

[0052] In contrast, in cases where the period of elapsed time measuredby the timer 11 is smaller than that of the period of activity time, thecontrol unit 12 tries to acquire positioning information from thesatellite signal reception unit 6 (step 209). Then the control unit 12begins a process to determine whether the positioning has been finishedor not (step 210). When the positioning has been finished, the controlunit 12 sends an “off” commands to the power switching unit 4 (step211), and outputs the positioning information to the not-shown externalsystem via the communication unit 13 (step 212). If the positioning hasnot been finished yet, the control unit 12 returns to the process atstep 206 to repeat the foregoing processing.

[0053] As explained above, in the satellite signal receiver according tothe second embodiment of the present invention, the period of activitytime is adjusted depending on a period of time elapsing from the lastpositioning. Thus the period of activity time can be approached or madeto agree to or with a remaining period of time to the next positioningto be expected as closer as possible, thereby a period of time to powerthe satellite signal reception unit being shortened. Useless consumptionof the power can be suppressed.

[0054] (Third Embodiment)

[0055] Referring to FIGS. 2 and 5, a third embodiment of the presentinvention will now be described.

[0056] A satellite signal receiver according to the third embodimentdiffers only in that the control unit 12 and the satellite signalreception unit 6 are constructed to perform further processing differentfrom that in the first embodiment. The remaining configuration andoperations of this satellite signal receiver are identical to those inthe first embodiment, so the differences with respect to the processingand operations are mainly described.

[0057]FIG. 5 is a flowchart showing power control for the satellitesignal receiver according to the third embodiment, which is executed byboth of the control unit 12 and the satellite signal reception unit 6.

[0058] When receiving a request for positioning issued outside throughthe communication unit 13 (step 300), the control unit 12 turns on thepower switching unit 4 in order to activate both of the satellite signalreception unit 6 and the timer 11 (step 301).

[0059] The calculation of a current position (i.e., positioning)requires that the signals from a given number of satellites necessaryfor the positioning be detected. In consideration of this, in thisembodiment, a period of activity time for signal detection is specified(step 302). Such period of signal-deception activity time is countedfrom at a time instant when the power switching unit 4 is turned on to atime instant when the signals from the given number of satellitesnecessary for the positioning are detected.

[0060] Then it is determined whether or not a period of elapsed timemeasured by the timer 11 is equal or larger to or than the period ofsignal-deception activity time (step 303). IF the determination is YESat step 303 (the signals from the given number of satellites necessaryfor the positioning have not been detected), the control unit 12 turnsoff the power switching unit 4 (step 304), then notifies the not-shownexternal system of an unsuccessful positioning through the communicationunit 13 (step 305).

[0061] By contrast, if the determination is NO at step 303 (the signalsfrom the given number of satellites necessary for the positioning havebeen detected within the period of signal-detection activity time), itis then determined whether or not the number of received satellitesignals is equal or larger to or than a necessary number (step 306). Incases the number of received satellite signals is equal or larger to orthan the necessary number, a period of positioning activity time, whichis counted from the turn-on of the power to positioning, is specified(step 307). However, if the number of received satellite signals islower than the necessary number, the processing is returned to step 303.

[0062] Subsequently the control unit 12 determines whether or not theperiod of elapsed time measured by the timer 11 is equal or larger to orthan the period of positioning activity time (step 308). If the periodof elapsed time measured by the timer 11 is equal or larger to or thanthe period of positioning activity time, the control unit 12 regards thepositioning as being impossible. In this case, in the same manner asabove, the control unit 12 turns off the power switching unit 4 (step304), then notifies the not-shown external system of an unsuccessfulpositioning through the communication unit 13 (step 305).

[0063] In contrast, in cases where the period of elapsed time measuredby the timer 11 is smaller than that of the period of positioningactivity time, the control unit 12 tries to acquire positioninginformation from the satellite signal reception unit 6 (step 309). Thenthe control unit 12 begins a process to determine whether thepositioning has been finished or not (step 310). When the positioninghas been finished, the control unit 12 sends an “off” commands to thepower switching unit 4 (step 311), and outputs the positioninginformation to the not-shown external system via the communication unit13 (step 312). If the positioning has not been finished yet, the controlunit 12 returns to the process at step 308 to repeat the foregoingprocessing.

[0064] As explained above, in the satellite signal receiver according tothe third embodiment of the present invention, the period of positioningactivity time is specified to regulate an interval from the turn-on ofthe power to the detection of all the signals necessary for thepositioning. This makes it possible to decide a condition in which thepositioning is impossible. Useless consumption of the power can besuppressed.

[0065] (Fourth Embodiment)

[0066] Referring to FIGS. 2 and 6, a fourth embodiment of the presentinvention will now be described.

[0067] A satellite signal receiver according to the fourth embodimentdiffers only in that the control unit 12 and the satellite signalreception unit 6 are constructed to perform further processing differentfrom that in the first embodiment. The remaining configuration andoperations of this satellite signal receiver are identical to those inthe first embodiment, so the differences with respect to the processingand operations are mainly described.

[0068]FIG. 6 is a flowchart showing power control for the satellitesignal receiver according to the fourth embodiment, which is executed byboth of the control unit 12 and the satellite signal reception unit 6.The processing shown in FIG. 6 is only different in step 407 from thatshown in FIG. 5.

[0069] In other words, in FIG. 6, when the number of received satellitesignals is equal or larger to or than the necessary number forpositioning, the control unit 12 clears the count of the timer 11 (step407), then specifies a period of activity time starting from thedetection of the signals to the next positioning (step 408).

[0070] As explained above, the satellite signal receiver according tothe fourth embodiment of the present invention adopts a period ofactivity time starting from the detection of all satellite signalsnecessary in number for positioning to the positioning, during whichtime the power is turned on. Thus the period of activity time can beapproached or made to agree to or with a remaining period of time to thenext positioning to be expected as closer as possible, thereby a periodof time to power the satellite signal reception unit being shortened.Useless consumption of the power can be suppressed.

[0071] (Fifth Embodiment)

[0072] Referring to FIGS. 2 and 7, a fifth embodiment of the presentinvention will now be described.

[0073] A satellite signal receiver according to the fifth embodimentdiffers only in that the control unit 12 and the satellite signalreception unit 6 are constructed to perform further processing differentfrom that in the first embodiment. The remaining configuration andoperations of this satellite signal receiver are identical to those inthe first embodiment, so the differences with respect to the processingand operations are mainly described.

[0074]FIG. 7 is a flowchart showing power control for the satellitesignal receiver according to the fifth embodiment, which is executed byboth of the control unit 12 and the satellite signal reception unit 6.The processing shown in FIG. 7 corresponds to the processing expressedby steps 406 to 408, which is a specification process of the period ofactivity time that starts from the signal detection to positioning. Theremaining part of the processing, though not shown in FIG. 7, isidentical to that shown in FIG. 6.

[0075] As shown in FIG. 7, from the satellite signal reception unit 6,the control unit 12 obtains information about the numbers of satellitesof which ephemeredes are memorized (step 501), then obtains informationabout the numbers of satellites from which signals are acquired (step502). Then determined is if or not only satellites from which thesignals have been received and ephemerides have been acquired are enoughfor calculation of positioning (step 503). If the determination is YES,a shorter period of activity time 1 is specified, because it will be nolonger necessary to acquire data to the ephemeris (step 504). But thedetermination is NO, that is, the present satellites of which signalshave been detected and of which ephemerides have been acquired are stillshort of satellites, a longer period of activity time 2 (> the period ofactivity time 1) is specified, for more ephemerides should be acquired(step 505).

[0076] In this way, the satellite signal receiver of this fifthembodiment is configured to adjust a period of activity time startingfrom the signal detection of all satellites necessary in number forpositioning to the positioning, depending on whether or not thepositioning requires acquisition of more ephemerides. Hence, the periodof activity time can be close or made agree to or with a remainingperiod of time to the next positioning to be expected. Accordingly, thepower is avoided from being consumed uselessly.

[0077] (Sixth Embodiment)

[0078] Referring to FIGS. 8 and 9, a sixth embodiment of the presentinvention will now be described.

[0079]FIG. 8 shows the configuration of a satellite signal receiveraccording to the sixth embodiment. Compared to the constituents shown inFIG. 2, a positioning-failure counter 16 of which count shows the numberof failures in positioning is added to be connect to the control unit 12and a power supply line from the power supply 3 to the timer 11 isadded. The control unit 12 is configured to perform a different type ofprocessing shown in FIG. 9. The remaining constituents and processingare the same or identical as or to those in the first embodiment, soonly such different elements will now be described mainly.

[0080]FIG. 9 outlines power control conducted by the satellite signalreceiver in the sixth embodiment.

[0081] In the present embodiment, the satellite signal reception unit 6is made to operate in an intermittent manner, so that the timer alwaysreceives power from the power supply 3 through the added power supplyline.

[0082] Thus, the timer 11 is subject to the determination whether or nota period of elapsed time measure by the timer 11 is equal or lager to orthan a predetermined intermittent reception interval (step 607). Whenthe determination is YES, that is, a period of elapsed time measure bythe timer 11 is equal or lager to or than the intermittent receptioninterval, the control unit 12 turns on the power switching unit 4 toactivate the satellite signal reception unit 6 as well as clear a countof the timer 11 (step 601).

[0083] Then it is determined if the period of elapse time measure by thetimer 11 is equal or larger to or than a period of activity time (step602). If the determination is YES at step 602, the control unit 12regards the positioning as being impossible. In this case, the controlunit 12 turns off the power switching unit 4 (step 603), then notifiesthe not-shown external system of an unsuccessful positioning through thecommunication unit 13 (step 604). The control unit 12 then increments acount of the positioning-failure counter 16 (the count is increased byone) (step 605).

[0084] By contrast, if the determination is NO at step 602 (the periodof elapsed time measure by the timer 11 is less than the period ofactivity time), the control unit 12 tries to read positional informationfrom the satellite signal reception unit 6 (step 608).

[0085] Then the control unit 12 begins a process to determine whetherthe positioning has been finished or not (step 609). When thepositioning has been finished, the control unit 12 sends an “off”commands to the power switching unit 4 (step 610), and outputs thepositioning information to the not-shown external system via thecommunication unit 13 (step 611). In this case, a count of thepositioning-failure counter 16 is set to zero (cleared; step 612). Ifthe positioning has not been finished yet, the control unit 12 returnsto the process at step 602 to repeat the foregoing processing.

[0086] After the positioning-failure counter 16 has been set at step 605or step 612, the intermittent reception interval is adjusted dependingon counts of the positioning-failure counter 16 (step 606). Forinstance, the internal is set to 10 minutes when a positioning-failurecounter's count is 2 or more, while it is set to 5 minutes when apositioning-failure counter's count is less than 2. As an alternativeexample, the period of activity time may be changed according to countsof the positioning-failure counter 16.

[0087] After adjustably setting the intermittent reception signal, thecontrol unit 12 determines, like the above, whether or not the period ofelapsed time measured by the timer 11 is equal to or over theintermittent reception interval that has been adjusted above (step 607).This determination is repeated if NO is kept at step 607.

[0088] If the determination is YES, that is, the period of elapsed timemeasured by the timer 11 reaches the intermittent reception interval,the processing is moved to step 601 to repeat the foregoing process.Namely, the power switching unit 4 is turned on to activate thesatellite signal reception unit 6 as well as clear the count of thetimer 11. As stated above, the satellite signal receiver of this sixthembodiment performs the power control similar to the first embodimentunder intermittent operations of the satellite signal reception unit 6.In this receiver, when the positioning cannot be conducted in series,the intermittent operation interval is widened. As a result, it istherefore possible to shorten a period of time to power the satellitesignal reception unit under a condition the positioning cannot beconducted, thus reducing useless consumption of the power.

[0089] (Seventh Embodiment)

[0090] Referring to FIGS. 8 and 10, a seventh embodiment of the presentinvention will now be described.

[0091]FIG. 10 outlines power control conducted by the satellite signalreceiver in the seventh embodiment. The processing in FIG. 10 is almostthe same as that shown in FIG. 9 except that step 705 is added afterstep 704 corresponding to step 604 in FIG. 9.

[0092] Specifically, after notifying the not-shown external system of anunsuccessful positioning through the communication unit 13 (step 704),the control means 11 determines whether or not the number of satellitesof which signals have been received is zero (step 705). If thedetermination is YES, that is, none of signals have been received fromany satellites, the positioning-failure counter 16 is incremented (step706). In contrast, at least one signal has been received from anysatellite (YES at step 705), the positioning-failure counter 16 iscleared to zero in its count (step 713).

[0093] As a result, in the satellite signal receiver according to theseventh embodiment, the power control identical to that explained in thefirst embodiment is performed with the satellite signal reception unitoperating intermittently. In this intermittent satellite signalreception, there is a possibility that any satellite signal cannot bereceived over a plurality of successive intermittent receptions. Suchoccasions occur when, for example, the receiver is located at particularplaces, such as being among city's buildings, which make the receptionof electric waves impossible or fairly difficult. In such a case, aperiod of time to supply the power is shortened through the processingat step 705, thus saving the power consumption.

[0094] For the sake of completeness, it should be mentioned that thevarious embodiments explained so far are not definitive lists ofpossible embodiments. The expert will appreciates that it is possible tocombine the various construction details or to supplement or modify themby measures known form the prior art without departing from the basicinventive principle.

What is claimed is:
 1. A satellite signal receiver comprising: asatellite signal reception unit for calculating a current position ofthe satellite signal receiver using an electric wave from a satellite,in response to a positioning request; a timer for clocking an elapsedtime in calculating the current position of the satellite signalreceiver; and power-on/off controlling means for controlling an on/offstate of power supplied to both the satellite signal reception unit andthe timer on the basis of information including the positioning request,the elapsed time clocked by the timer, and a condition under which thesatellite signal reception unit receives the signal from the satellite.2. The satellite signal receiver according to claim 1, furthercomprising a communication unit for receiving the positioning requestgiven from an external system and transmitting information about thecalculated current position to the external system.
 3. The satellitesignal receiver according to claim 1, wherein the power-on/offcontrolling means includes: switch means for switching on or off thepower supplied to both the satellite signal reception unit and thetimer; and control means for controlling turn on/off operations of theswitch means based on the information.
 4. The satellite signal receiveraccording to claim 3, wherein the satellite signal reception unitincludes memory means for memorizing the calculated positionalinformation including the number of ephemerides serving as dataconcerning an orbit of the satellite orbit, and the information aboutthe condition is information about the number of ephemerides.
 5. Thesatellite signal receiver according to claim 4, wherein the controlmeans includes first control means for turning on the switch means inresponse to the positioning request, setting means for adjustablysetting a period of active time counted from a first time instant atwhich the switch means turns on to a second time instant at which thesatellite signal reception unit calculates the current position, andsecond control means for turning off the switch means when the elapsedtime reaches the period of active time.
 6. The satellite signal receiveraccording to claim 5, wherein the setting means is configured so thatlarger the less the number of ephemerides, the larger the period ofactive time.
 7. The satellite signal receiver according to claim 3,wherein the satellite signal reception unit includes memory means formemorizing the calculated positional information including the number ofephemerides serving as data concerning an orbit of the satellite orbitand clock means for clocking a positioning time for the calculation ofthe current position, and the information about the condition isinformation about an elapsed time from the last calculation of thecurrent position obtained using the clock means.
 8. The satellite signalreceiver according to claim 7, wherein the control means includes firstcontrol means for turning on the switch means in response to thepositioning request, setting means for adjustably setting a period ofactive time counted from a first time instant at which the switch meansturns on to a second time instant at which the satellite signalreception unit calculates the current position, and second control meansfor turning off the switch means when the elapsed time counted by thetimer reaches the period of active time.
 9. The satellite signalreceiver according to claim 7, wherein the control means includes firstcontrol means for turning on the switch means in response to thepositioning request, setting means for setting a period of active timecounted from a first time instant at which the switch means turns on toa second time instant at which the satellite signal reception unitreceives the electric waves necessary in number for the calculation ofthe current position, and second control means for turning off theswitch means when the elapsed time counted by the timer reaches theperiod of active time.
 10. The satellite signal receiver according toclaim 7, wherein the control means includes first control means forturning on the switch means in response to the positioning request,setting means for setting a period of active time counted from a firsttime instant at which the satellite signal reception unit receives theelectric waves necessary in number for the calculation of the currentposition to a second time instant at which the satellite signalreception unit calculates the current position, and second control meansfor turning off the switch means when the elapsed time counted by thetimer reaches the period of active time.
 11. The satellite signalreceiver according to claim 4, wherein the control means includes firstcontrol means for turning on the switch means in response to thepositioning request, setting means for adjustably setting a period ofactive time counted from a first time instant the satellite signalreception unit receives the electric waves necessary in number for thecalculation of the current position to a second time instant at whichthe satellite signal reception unit calculates the current position, andsecond control means for turning off the switch means when the elapsedtime reaches the period of active time.
 12. A satellite signal receivercomprising: a satellite signal reception unit for intermittentlycalculating a current position of the satellite signal receiver atadjustable intermittent intervals by using an electric wave from asatellite; a timer for clocking an elapsed time every time when thecurrent position of the satellite signal receiver is calculated; andpower-on/off controlling means for intermittently controlling an on/offstate of power supplied to the satellite signal reception unit on thebasis of information including the elapsed time clocked by the timerevery time when the current position of the satellite signal receiver iscalculated.
 13. The satellite signal receiver according to claim 12,wherein the power-on/off controlling means includes means fordetermining whether or not the elapsed time clocked by the timer reachesa given period of time with no completion of a positioning process andmeans for commanding the off state of the power when the elapsed timereaches the given period of time with no completion of the positioningprocess.
 14. The satellite signal receiver according to claim 12,wherein the power-on/off controlling means includes a counter forcounting the number of failure in calculating the current position andmeans for adjusting the intermittent intervals depending on the count ofthe counter.
 15. The satellite signal receiver according to claim 14,wherein the adjusting means is configured to make the intermittentintervals longer when it is impossible to calculate the current positionin succession.
 16. The satellite signal receiver according to claim 14,wherein the adjusting means is configured to make the intermittentintervals longer when the satellite signal reception unit is impossibleto receive the electric wave from any satellite in succession.